The present invention relates to a multifunction speaker used in a mobile transmission instrument such as a portable telephone and pager. The multifunction speaker is provided with a sound emanating function and vibrating function device for informing a user when a calling signal is applied.
A conventional mobile transmission instrument such as a portable telephone is generally adapted to change the operation thereof from generating buzzer sounds and melodies to vibrating a case of the instrument without producing sounds for informing the user of a calling signal. In order to achieve that kind of operation, a small speaker for generating sounds and a vibrating device in which an eccentric weight is vibrated by the rotation of a small motor are provided separately in a mobile transmission instrument. However, incorporating both the speaker and the vibrating device in the instrument is disadvantageous in rendering the instrument compact and inexpensive. Thus, there has been provided a multifunction speaker capable of generating both the sounds and the vibration within a single device such as that described in FIG. 1 and pages 3 to 4 in the specification of Japanese Patent Application Laid-Open 2001-231096.
FIG. 5a is a plan view of that kind of conventional multifunction speaker mentioned above, and FIG. 5b is a sectional view taken along a line V-V of FIG. 5a. 
Referring to FIGS. 5a and 5b, a case of the multifunction speaker comprises an upper frame 22 and a lower frame 21 made of resin and houses a magnetic circuit 23 therein. The magnetic circuit 23 comprises a pole piece 24 made of a magnetic material and having a center pole 24a and a flange 24b, annular magnet 25 made of such a material as samarium-cobalt attached to the flange 24b by such a means as adhesive, and an annular magnetic top plate 26 adhered to the magnet 25.
An upper supporting spring plate 27 is attached to the upper frame 22 by means such as adhesive and insert molding. The inner periphery of the spring plate 27 is attached on the outer edge of the top plate 26 by point welding and other means thereby to resiliently support the top plate 26. A part of the spring plate 27 is extended beyond the case to form a ground terminal 27a. The ground terminal 27a is provided to conduct static electric charges in the magnetic circuit 23 harmlessly to earth so as to prevent damage caused by electrostatic discharge.
The magnetic circuit 23 is further supported by a lower spring plate 28. More particularly, the outer periphery of the lower spring plate 28 is securely attached to the lower frame 21 and the inner periphery is securely attached to the pole piece 24 by point welding, for example.
A diaphragm 29 is mounted on the inner periphery of the upper frame 22 at the outer periphery thereof. A cylindrical coil 30 which is secured to a lower part of the diaphragm 29 is inserted in a magnetic gap formed between the outer periphery of the center pole 24a and the inner periphery of the top plate 26. The ends of the coil 30 is connected by solders to a pair of terminals 31 provided on the upper frame 22 for connecting the coil 30 to an external circuit. A magnetic ring 32 is further provided in the case for shielding the magnetic circuit 23 so that the generated magnetic field is prevented from leaking out of the case.
In operation, when a driving signal of audio frequency is applied to the coil 30 through the terminals 31, the cylindrical coil 30 alternatingly generates an electromagnetic force to vibrate the diaphragm 29, thereby to generate sounds. When the frequency of the applied signal is low, while no sound is generated from the diaphragm 29, the magnetic circuit 23 supported by the upper and lower spring plates 27 and 28 is mechanically vibrated. The vibration is transmitted through the case to the equipment in which the multifunction speaker is housed so that the user is able to feel the vibration and be informed of a phone call.
In the conventional multifunction speaker, when mounting the magnet 25 on the flange 24b of the pole piece 24, since there is no positioning guide for the magnet, the magnet tends to be diverged from the adhering position. In addition, there is a problem that the magnet and the pole piece often come apart during a drop shock test.